BACKGROUND: The development of Graves' disease (GD) from Hashimoto's thyroiditis (HT) has sporadically been reported, but no data are available concerning the prevalence of this sequence of events in GD patients. Our aim was to ascertain HT antecedents in the history of GD children in order to assess for the first time the relative frequency of the event sequence leading from HT to GD in a pediatric population. STUDY POPULATION AND
RESULTS: In 105/109 patients, no HT antecedents were documented at GD presentation. The remaining 4 patients had previously exhibited a picture of HT with either hypothyroidism or euthyroidism. The interval between HT diagnosis and GD presentation ranged from 1.5 to 2.8 years. Serum thyrotropin receptor antibodies were higher in the patients with no HT antecedents.
CONCLUSIONS: In at least 3.7% of the children with GD, hyperthyroidism may be preceded by HT presentation with either hypothyroidism or euthyroidism. The clinical course of GD in these patients is not different from the one observed in those with no HT antecedents. Our report confirms the existence of a continuum between HT and GD within the spectrum of autoimmune thyroid diseases.

BACKGROUND: The development of Graves' disease (GD) from Hashimoto's thyroiditis (HT) has sporadically been reported, but no data are available concerning the prevalence of this sequence of events in GD patients. Our aim was to ascertain HT antecedents in the history of GD children in order to assess for the first time the relative frequency of the event sequence leading from HT to GD in a pediatric population. STUDY POPULATION AND
RESULTS: In 105/109 patients, no HT antecedents were documented at GD presentation. The remaining 4 patients had previously exhibited a picture of HT with either hypothyroidism or euthyroidism. The interval between HT diagnosis and GD presentation ranged from 1.5 to 2.8 years. Serum thyrotropin receptor antibodies were higher in the patients with no HT antecedents.
CONCLUSIONS: In at least 3.7% of the children with GD, hyperthyroidism may be preceded by HT presentation with either hypothyroidism or euthyroidism. The clinical course of GD in these patients is not different from the one observed in those with no HT antecedents. Our report confirms the existence of a continuum between HT and GD within the spectrum of autoimmune thyroid diseases.